The present invention relates to a device for continuous adjustment of the vibration amplitude of eccentric elements especially designed for soil and asphalt compaction machines.
In the compaction of soil, asphalt and similar materials by means of vibratory rollers, it is often necessary to adapt vibration amplitude to the nature of the bedding in order to achieve the desired compaction effect. As a rule, greater amplitude results in a higher compaction effect across the entire vibration frequency range. This applies in particular to blast stone, stony moraine and cohesive soils. In the final stages of the compaction process, however, it often happens that the machine begins to run irregularly which results in high stresses in all of its parts. By reducing vibration amplitude in the final compaction stages, the irregular motion of the machine can be cured. Thus for every type of bedding it is possible to obtain the maximum compaction effect for the type of compaction machine in use, and at the same time, overcompaction can be avoided or at least reduced. A prerequisite for this operation is the use of a vibration element with continuously adjustable amplitude. It is also necessary that adjustment of the machine can be carried out in such a manner that it is possible to determine with certainty the magnitude of an arbitrarily set vibration amplitude.
Achieving continuous amplitude adjustment by means of hydraulically or electrically powered systems is already known. These systems are often complicated, however, and adjustment cannot as a rule be achieved under all operating conditions. In certain hydraulic systems the volume of oil under pressure is also in rotation, which necessitates a rotary seal with the danger of leakage and troublesome heat generation in the oil as a result.